Resistant Starch May Reduce Red-Meat Colorectal Cancer Risk

Eating high amounts of red meat increase risk of colorectal cancer while fiber-filled food reduces the risk, AICR research shows. Now comes a study that offers one possible explanation for both links, finding that diets high in red meat and a type of non-digestable fiber have opposite effects on a group of genetic molecules.

Study researchers focused on a type of fiber called resistant starch. Our bodies don’t digest resistant starch in the small intestine. Then in the gut, bacteria convert resistant starch into the compound butyrate. In lab studies, this compound protects against colon cancer.

For the study, 23 participants, ages 50 to 75, switched between two types of diets. In one diet each person was given 300 grams — about 10 ounces — of raw lean red meat a day. That’s about the equivalent of a cooked 8 ounce burger. The other diet had the same red-meat content plus a butyrate resistant starch formulation. Each person was on one diet for four weeks then after a four-week washout period, switched to the second diet for four weeks.

Participants were asked to eat normally for all other parts of their diet, except to avoid eating lots of protein, fiber, and probiotic supplements.

After eating each diet, researchers looked at certain microRNA molecules that previous research has shown may play a role in colorectal cancer. Higher levels of these microRNA molecules were seen in colorectal cancer.

In the high red-meat diet alone, some of the molecules were increased in participants’ rectal tissue. They also had an associated increase in cell proliferation. When the participants ate the red meat plus the butyrate resistant starch, the levels of the molecule were lower and butyrate higher.

The study has several caveats, including the small number of participants. Individuals’ differences in microRNA levels limits any firm conclusions, the authors note. It’s also unclear what in red meat or the resistant starch formation may have altered the microRNA. This study also used a supplement of resistant starch, not foods containing it.

But it adds to the growing research on resistant starch and butyrate. If you want to eat more resistant starch, you’ll find it in beans, potatoes and a variety of grains, along with other starch-containing plant foods. Of course, eating high amounts of all foods containing fiber links to reduced risk of colorectal cancer. Being physically active and staying a healthy weight also reduce risk.